Illustration by Garry Marshall

A ceiling-mounted sensor “sees” who’s in the car and inflates airbags to the appropriate size.

This fall, more than a third of new cars must, by federal mandate, be able to sense the difference between an adult occupant, a child and an empty seat. Airbags would then only inflate as much as needed. Weight and tension sensors under seats and in seatbelts are the first step, but Siemens, TRW and Motorola are developing lasers, 3-D cameras and electrical fields that can determine occupants’ position as well as their size. “The existing technology can determine if someone’s in a seat,” notes TRW engineer Roger McCurdy, “but the real value will be when airbags determine when someone is out of position — that’s the root cause of injuries.”